Retained Placenta After a C-Section

A retained placenta after cesarean section occurs when part or all of the placenta fails to separate cleanly from the uterine wall after the baby is delivered. During a C-section, surgeons typically wait for the placenta to detach on its own or gently assist its removal, but sometimes the tissue stays firmly embedded in the muscle of the uterus. This is more common than many people realize, and women who have had a prior C-section face a higher risk of it happening in a subsequent delivery. The reasons involve scarring, abnormal placental attachment, and a spectrum of severity that ranges from a mild inconvenience to a surgical emergency.

How the Placenta Normally Separates During a C-Section

After the baby is lifted out through the uterine incision, the uterus immediately begins contracting and shrinking. As the muscle wall compresses, the placental bed becomes smaller than the placenta itself. That mismatch creates a shearing force that peels the placenta away from the wall and simultaneously squeezes the newly exposed blood vessels shut, limiting blood loss. This is why many surgeons prefer to let the placenta separate on its own rather than pulling it off by hand. A meta-analysis of randomized trials found that spontaneous separation during C-section tends to result in less blood loss than manual removal, precisely because the natural contraction-and-shear mechanism is more orderly.

When this process fails, the placenta either does not separate at all or separates incompletely, leaving fragments behind. The retained tissue continues to occupy the uterine wall, and the blood vessels that were feeding it remain open. That is where the danger begins.

Why a Previous C-Section Raises the Risk

A prior cesarean delivery leaves a scar on the uterus. In subsequent pregnancies, the placenta may implant directly onto or near that scar tissue, where the normal uterine lining has been replaced by fibrous tissue that lacks the regulatory signals needed to keep placental growth in check. A large population-based study found that women with a previous C-section had a retained-placenta rate of about 3.4%, compared with roughly 2% in women whose earlier deliveries were vaginal. The association was even stronger when the retained placenta came with heavy bleeding.

The C-section scar is not the only thing that matters. A separate population-based study found that any history of intrauterine procedures substantially increases the odds. Prior curettage (a scraping procedure sometimes used after miscarriage) carried the highest risk, while previous C-section and complications like pre-eclampsia, delivering a very small baby, or stillbirth were also significant predictors.

Each additional C-section adds another scar, and the cumulative scarring can create a progressively more hostile environment for normal placental attachment. This is one reason obstetricians discuss the risks of multiple repeat cesareans carefully with patients planning large families.

The Placenta Accreta Spectrum

When a retained placenta is more than just sluggish separation, the diagnosis often falls somewhere on the placenta accreta spectrum, or PAS. In these cases, the placenta does not merely sit on the uterine lining; it grows into, and sometimes through, the muscle wall. Uterine scarring disrupts the normal signals that ordinarily tell trophoblast cells (the placenta’s invasive front line) where to stop. Without those inhibitory cues, the placenta burrows deeper than it should.

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An expert classification system grades PAS by how deep the invasion goes:

Grade 1 (noninvasive): the placenta is abnormally stuck to the wall but has not penetrated the muscle. The muscle underneath looks normal in thickness.
Grade 2 (superficial invasion): placental tissue has grown partway into the muscle, but the outer wall is still intact with at least a quarter of its normal thickness preserved.
Grade 3A (deep invasion): the placenta reaches nearly through the full muscle wall, leaving less than a quarter of the normal thickness intact, though the outer surface of the uterus is still unbroken.
Grade 3D (deep with serosal disruption): the invasion breaks through the outer surface of the uterus.
Grade 3E (extrauterine invasion): the placenta has grown into a neighboring organ, most often the bladder.

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The severity matters enormously for surgical planning. A Grade 1 case might be managed by carefully removing the adherent tissue. A Grade 3E case, where the placenta has invaded the bladder, often requires a multidisciplinary team and may end with a hysterectomy.

Detecting the Problem Before and During Surgery

Ideally, abnormal placental attachment is identified before the delivery even begins. Ultrasound is the first-line screening tool, and MRI can add detail when ultrasound findings are unclear. Together, these imaging methods can reveal telltale signs like increased blood flow to the scar area, thinning of the uterine wall, or placental tissue that appears to extend beyond the expected boundary.

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When PAS is suspected in advance, the surgical team can prepare accordingly. Current guidelines recommend that surgeons perform a thorough visual survey of the uterus and pelvis upon entering the abdomen, looking for abnormal blood vessels or distorted anatomy. The hysterotomy incision is deliberately placed well away from the placental edge, and after the baby is delivered, the relationship between placenta and muscle is assessed directly before anyone attempts removal.

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Not all cases are caught ahead of time, though. One study of women with placenta previa (where the placenta covers the cervix) found that placental adherence was dramatically more likely when the placenta sat directly on a previous C-section scar and when ultrasound showed no clear zone of separation between placenta and muscle wall.

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What Happens When the Placenta Will Not Come Away

If the surgical team encounters a placenta that refuses to separate, the next step depends on the severity of the attachment and how much the patient is bleeding. The options range from conservative approaches that preserve the uterus to emergency hysterectomy.

Leaving the Placenta in Place

In some cases, particularly when the invasion is deep but bleeding is controlled, surgeons choose to close the uterus with the placenta still inside and let it resorb over weeks to months. In one series of 50 women planned for this approach, the vast majority (86%) were successfully managed without removing the uterus. Among those 43 women, about 12% later needed a hysterectomy because of delayed bleeding, and roughly 9% developed uterine infection. There were no maternal deaths.

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Leaving the placenta in situ requires close follow-up, often for months, as the tissue slowly breaks down. A multicenter retrospective study concluded this could be a viable uterus-preserving option for women with PAS who have no active hemorrhage at delivery, though it demands vigilant monitoring.

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Surgical Removal With Uterine Preservation

When the abnormal tissue is confined to a limited area of the uterine wall, a surgeon may be able to cut out just the affected segment and repair the uterus. One reported approach involved removing a roughly 10-centimeter area of placenta that had grown through the anterior wall, excising it with electrocautery, and then closing the defect.

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More complex techniques combine tourniquets on the uterine blood supply with balloon tamponade inside the uterine cavity, followed by resection of the invaded wall and double-layered repair. These methods are technically demanding but offer an alternative to hysterectomy for women who want to preserve their fertility.

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Hysterectomy

When bleeding is uncontrollable, or the placenta has invaded deeply enough that no repair is feasible, removing the uterus becomes the safest path. Emergency peripartum hysterectomy for PAS is a major operation. One 10-year series documented an average blood loss of about 3,800 mL (roughly equivalent to losing almost the entire blood volume), with patients receiving an average of 15 units of blood transfusion and spending about eight days in the hospital.

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Timing matters a great deal. A study comparing emergency versus electively scheduled cesarean-hysterectomies for PAS found that emergency cases had nearly double the blood loss, dramatically higher rates of coagulopathy (a dangerous inability to form blood clots), and a much greater chance of bladder injury.

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This is the central argument for prenatal diagnosis. When a team knows PAS is coming, the surgery can be scheduled with the right specialists in the room, blood products ready, and interventional radiologists standing by. Arterial catheterization and embolization, where small particles are injected to block blood flow to the uterus, can be performed during or after surgery to control hemorrhage and may sometimes eliminate the need for hysterectomy altogether.

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Hemorrhage and Acute Complications

Severe bleeding is the defining threat. When PAS is managed at an experienced center with a coordinated protocol in place before the incision, outcomes improve substantially. A retrospective study comparing different management approaches found that women treated under a systematic preoperative plan had significantly less total blood loss, fewer blood transfusions, shorter hospital stays, and lower rates of both coagulopathy and organ injury compared with those managed in less structured ways.

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The anesthesia team plays a critical role in these cases. Massive transfusion protocols, where red blood cells, plasma, and platelets are given in rapid sequence, are often activated. One case report of a cesarean hysterectomy for deeply invasive placenta described eight liters of postpartum blood loss requiring 16 units each of red blood cells and fresh frozen plasma, plus additional platelets and clotting factors.

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Infection Risk When the Placenta Stays Behind

Whether placental tissue is intentionally left in place or fragments are unknowingly retained, infection is a serious concern. One case report described a woman managed conservatively after placenta accreta who developed persistent fever and elevated white blood cell counts despite weeks of antibiotic treatment. When the retained tissue was eventually evacuated by curettage, she went into septic shock.

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That case represents the worst outcome, but it is not the norm. A cohort study tracking women who had their placenta deliberately left in situ found that while many developed positive bacterial cultures from the cervix or urine (most commonly E. coli and related bacteria), the infections were generally manageable with antibiotics. None of the women in that series required a secondary surgery because of infection. The researchers noted that postpartum discharge, mild fever, and elevated inflammatory markers in these patients do not always indicate a dangerous infection and can often be treated without reoperation.

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Delayed Bleeding After Discharge

Retained placental tissue does not always announce itself during the delivery. Some women develop secondary postpartum hemorrhage, meaning significant bleeding that starts more than 24 hours after birth. In a study conducted in a setting with a high C-section rate, retained placental tissue accounted for about 21% of secondary hemorrhage cases, second only to uterine infection as a cause. Ultrasound correctly identified retained tissue in many of these women, and when surgical evacuation was performed, pathological examination confirmed the diagnosis about 71% of the time.

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This means that if you have had a C-section and experience heavy or increasing bleeding days or weeks later, retained tissue is one of the first things your care team will investigate. You should not assume postpartum bleeding is normal indefinitely. A sudden increase in flow, passage of large clots, or bleeding that soaks through a pad in under an hour warrants urgent evaluation.

What Retained Placenta Means for Future Fertility

One of the under-discussed consequences of retained placenta is the risk of intrauterine adhesions, sometimes called Asherman’s syndrome. When placental remnants are removed by curettage, the scraping can damage the uterine lining. A prospective study that performed follow-up hysteroscopy three months after secondary removal of placental remnants found intrauterine adhesions in 40% of patients. Among women who had menstrual irregularities after the procedure, the risk of moderate-to-severe adhesions was about twelve times higher than in those with normal periods.

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Adhesions can cause lighter or absent periods, pain, and difficulty getting or staying pregnant. If you have undergone curettage for retained tissue and notice a significant change in your menstrual pattern afterward, bring it up with your provider. Early detection through hysteroscopy allows the adhesions to be divided before they become dense and difficult to treat.

For women who had PAS managed conservatively and went on to conceive again, the picture is cautiously optimistic. A retrospective cohort study followed 72 women through 75 subsequent pregnancies after conservative PAS treatment. Among those who reached full or near-term delivery, all newborns survived. However, recurrent PAS occurred in about 23% of those deliveries, and cesarean scar pregnancies, where the embryo implants directly in the old scar, occurred in 8% of subsequent pregnancies overall.

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Postpartum hemorrhage itself tends to recur. One review noted that a previous episode of postpartum hemorrhage is one of the strongest predictors of it happening again, possibly because the same underlying risk factors, including retained placenta and uterine scarring, persist from one pregnancy to the next.

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Why Center of Care Matters

If there is one practical takeaway from the research on retained placenta and PAS after C-section, it is that where you deliver can make a meaningful difference. The gap in outcomes between emergency and planned surgery for PAS is stark: emergency cases see roughly double the blood loss, coagulopathy rates jumping from around 6% to 40%, and bladder injury rates climbing from 13% to 44%.

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Centers that manage PAS routinely assemble teams that include maternal-fetal medicine specialists, experienced surgeons, interventional radiologists, anesthesiologists skilled in massive transfusion, and neonatologists. Having these people in place before surgery, rather than scrambling to page them during a hemorrhage, is what drives the better numbers. If your ultrasound raises any suspicion of abnormal placental attachment, particularly if you have had a prior C-section, ask about referral to a center with PAS experience. That conversation may be the most consequential thing you do before your delivery date.